Gang rape videos on sale in India | Reuters

MUMBAI (Thomson Reuters Foundation) - Graphic mobile phone clips of gang rapes are being sold in shops in Uttar Pradesh, as a spate of rapes in one of the country's most violent states has sparked anger and calls for the chief minister to step down.

The clips, which last 30 seconds to five minutes, are being sold in the "hundreds, perhaps thousands, every day", the Times of India reported. They cost 50-150 rupees ($0.75-$2) each.

"We are aware. We are taking necessary action. But it is difficult, as the sales are happening below the counter," Ajay Sharma, a deputy inspector general of police in the city of Agra, told the Thomson Reuters Foundation.

In recent weeks, several gang rapes have been reported in Uttar Pradesh, which ranks among the most unsafe for women.

Last week, a woman and her 14-year-old daughter were dragged from their vehicle at gunpoint on a major highway and gang-raped for hours in nearby fields. Local media reported that initially the police did not respond to a call for help.

The Indian Express reported that this week another woman was gang-raped in Uttar Pradesh, and said the incident had been recorded on a mobile phone.

Increasingly, perpetrators are recording their crimes on mobile phones to use as a blackmailing tool and to dissuade victims from going to the police, the Times of India said.

Chief Minister Akhilesh Yadav has come under fire over the rise in violent crimes against women, with #LawlessUP trending on Twitter this week.

In 2014, there were 337,922 reports of violence against women including rape, molestation and abduction, a 9 percent increase on the previous year, according to official data.

During lengthy trials, victims and their witnesses are sometimes intimidated by the accused who, in some cases, are granted bail by the court.

A wave of public protests following the fatal gang-rape of a woman on a Delhi bus in December 2012 prompted the government to enact stiffer penalties, including the death sentence for repeat rape offenders and the criminalisation of stalking.